Nullifying disturbances in telegraphic or other signaling circuits.



m- 874,826. PATENTED m0 24, 1907.

E. BLAKENEY &'R. E. OHETW0OD,-JR. NULLIFYING DISTURBANGES IN TELEGRAPHIOOR OTHER SIGNALING CIRCUITS,

APPLICATION-FILED M1229, 190s.

mum-H1 SW i sumes such a' undulatory character that the ceiving elementsand thus prevent this dis- T 0 all whom it may concern:

earns Parana: ems-a EDWARD BLAKENEY, OF OSSINING, NEWYORK, AND ROBERT EvCHETWOOD, JR, OF ELIZABETH, NEW JERSEY, ASSIGNORS TO AMERTUAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Dec. 24,1907.

Application filed May Z9,1906. Serial No. 319388.

Be it known that we, EDWARD BLAKENEY l and ROBERT E. Cnn'rwoon, Jr.,residing at Ossining and Elizabeth, in the counties of Vlestchester andUnion and States of New Yuri-a and New Jersey, respectively, haveinvented certain Improvr-snusnts in Nullifying Disturbances in 'lelegra'ihic or other Signaling C1 rcuits, of which the following is a specificatien.

This invention has reference to the separation oi currents of difierentcharacters flowing in electrical circuits, and particularly to thenullifying of such disturbancesas may be produced in telegraphic orother signaling circuits by the inductive effect of an adj accnt circuitcarrying an alternating current.

Considering a telegraph system in which the relays or other receivingelements are operated by the presence or absence of directv current, itbeing organized for operation by the normal slowly recurring currentimpulses of standard Morse signals manually transmitted, if the line hasnear it a conductor through which passes an alternating current, asimilar current will be induced in the telegraph-line which will besuperposed upon the operating current. A class of alternating currentwhich is at the present time often encountered is that of single phaseand of comparatively low frequency yet high relatively to Morsetransmission, say 25 cycles per secend, which is employed for powertransmission. The electromotive forces producing such currents areusually extremely high, and, of course, change abruptly from theirmaximum value to zero, giving powerful inductive effects, yet thefrequency is not so great but that the armaturcs of the relays canfollow the alternations induced in the line. As a result the operatingcurrent assignals are d started and. confused by the vibratlon of thearmatures. To exclude the alternating current from the telegraphicreturban'c, and to provide a system by which, signals may beeil'ectively tral'ismitted and received without interference orconfusion are the principal objects of the invention.

It consists in a means for furnishing separate paths for and confiningthereto currents of diverse characteristics, that which. is hereindisclosed being in the form of a balance circuit with which thereceiving element is associated and which excludes alternating currentfrom said receiving element by virtue oi the establishmentof a conditionof equipotential at the extremities of a bridge or cross conductor inwhich it is placed, while the bridge is thrown out of equilibrium for 0erating currents and made a portion of tieir exclusive path by thepresence of inductive devices in a portion or the branches of thebalance circuit to which telegraph currents are relatively impassable.

In order that the invention may be more readily understood, reference ishad to the accompanying drawings.

' Figure 1 illustrates diagrammatically a specti'v'ely, to behereinafter more particularly referred to, and between which extends,

a line conductor L. This conductor is shown 80 as grounded at its,extremities to complete the main circuit, though obviously a completemetallic circuit could be substituted if desired, and ,containsbatteries 1) or other suitable-sourees of operating current.

Situated in sucli proximity to the line as to act inductively upon it,is shown a conductor L constituting, for example, a portion of apower-circuit and carrying an alternating current flowing from agenerator or other source G, which is of such periodicity that adisturbance will be produced in the telegraph line prejudicial to itsoperation.

To nullify the effect of parasitic or disturbing currents andprevent thereceiving instruments r, whichappear conventionally in the drawings asrelays, from being affected thereby, the line L at each station isdivided, there being two conductors 10 and 11 connected in parallel toform a section or exten sion of the main circuit they being in seriestherewith. These parallel branches of the line are s arated intoportions 0, d, c and f by a bri ge-conductor 12 connecting the points a:and y in the conductors 10 and 11, respectively, and in thebridge-conductor of each station is connected its relay r. Each of theseportions 0, (Z, e, and f when 'eferred telegraph system arranged. inaccordance c, d, e,ff the conductors and 1 1 furnishmg the sides, whilethe conductor 12 rovides the cross wire or bridge. As wel -known, Whenthe fall of potential in, say, the side 0 of-the balance is to that inthe side e as the fall in the side (1 is to that inlhe side f, thepoints a: and y will be of equal potential and no current will flowthrou h or rather the most convenient.

electromot'ive torces are balanced in the bridge. Therefore, to nullifythe disturbing efiect of the energy existing in the conductor- L whilestill permitting telegraphic operation, it is onl necessary to secureequality of potential or-alternating currents, while for direct currentsthe bridge is unbalanced. This result may be attained by so adjustingthe impedance of each side that with refers 5: will be satisfied, and byemploying in the conductors 10 and 11 at opposite sides of the bridgeinductive devices such as condensers which are opaque or impassable todirect currents while transparent or permissive to alternating currents,and including in the companion sides impedance devices allowing currentsof both characteristics to pass. In each of the sides 0 and f of thebalance-circuit are shown coils I possessing both resistance andinductance, this being referably adjustable, and in series with t 1ecoils l in diagonally opposite portions of the parallel branches arecondensers C which are shown as being of variable capacity. In each armd and e is a suit 7 able resistance R, also preferably adjustable, whichmay or may not be inductive, as is \Vhen the impedance in the varioussides is balanced in the manner previously stated, the bridge 12 will benew tral to the induced alternating currents, which will flow throughboth parallel c0nductors 10 and 11 passing inductively through thecondensers, and to ground through the battery, leaving therelaysunaiiected But upon making and breaking the main circuit by meansof one of the keys the impulses will pass through the line, and sincethe condensers are conductively (liscontinuous for, or are impassable todirect ence thereto the equation .slow-changing currei'its, the circuitis unbalanced as far as these are concerned and they flow e-Xcusivelythrough the sides d and e and the bridge-connection those constitutingthe sole conducting path through the balance the disturbing tion ifslight V This may be determined experimentally, or

v be used'in t manner.

In balancing the circuit the frequency of current should be considered,

and, as this is liable to vary, such values of x resistance, inductance-and capacity should be chosen as will not greatly disturb itsequachanges in frequency occur.

mathematically by use of t e formula:

by substituting various values of resistance" (r), inductance (l), andcapacity (0), until such are found that the impedance will vary butlittle for the expected fluctuation in the frequency (n). In any eventthe resistance in the sides (2 ends should be kept as low as possible toavoid cutting down. the operating currents they carry. Also, ifpractical, that is if such devices for any specific case are not undulylar e, air-core coils may preferably 1e sides 0 andf, as is illustratedat station A, since their inductance is reasonably constant within awide range of practical conditions, and with non-inductive resistance inthe arms d and e the circuit would remain substantially balanced for anyparticular frequency, regardless of the magni tude of the inducedcurrent. It may be found, however, that to secure the necessaryinductance air-core coils are too cumbersome, and in such case thosehavingiron cores may be employed as is shown at station B. c

There are four po'rtionsof the circuit in which each of the keys is maybe placed to effect the transmission of signals-in the bridge 12, Fig.3, in the line outside the bal ance-circuit, Fig. 2, or in traverse. Iflocated in the first-named position the key is shunted by two circuitsof large capacity furnished by the arms 0 d an i e f, respectively, sothat although the relay of the sending-operator may respond properly,that of the distant statidn will be sluggish. With the key in the line,ii. the circuit is not properly balanced some of the alternating currentmay pass through the bridge and the operating current therein becomesmore or less undulatory. This being the case the action of the relay isliable to be irregular, as the key may be closed, considering theextremes, at either the period of maximum or minimum current. The mostadvantageous location for the key is in one of the sides (1 or 0, sincewhen said hey is open the condenser in the other branch conductor ischarged by the line batteries and upon closure is discharged, giving astrong current impulse which is suf- 'icient to overcome any laggingtendency of the line current.

llt.

In connection Witheach of iv either ,one of the I sides d or e which theoperating currents the keys is shown the usual circuit closer or quencyinduced currents, comprising two swrtchdc? by wlneh the continuityof thecir- 5 cult may be-preservedwhen ,the operators 2 are not transmitting,The. switch at the station B appears as open; or in the positionfor'transmission.

Having thus deseribed the invention, we claim:

1. In a telegra hic circuit organized for operation by the. sihwlyrecurring current impulses of' manually transmitted Morse signals, thecombination of a line conductor; branches in parallel with one anotherforming jointly an extension of said line conductor in series therewith;a bridge conductor uniting said parallel branches; an inductiveconnection in each parallel branch on different sides of the saidbridge, respectively, rendering such portion-of each branch impassableto steady currents and to the said slowly recurring normal currentimpulses,

' but permitting the passage therethrough of relatively high frequencyinduced alternatingcurrents; and means for maintaining a potentialdifference at the extremities of said bridge for the said normalcurrents, and a condition of equipotential for said induced currents.

v 2. A tele raph system comprising a main circuit, a W eatstone-balancesystem having its branches connected in the main circuit, a

receiving instrument in the brid e of the balance, and a condenserconnecte in a I ortion of each branch at each side of the bri go, andrendering said portions impassable to steady currents.

3. A telegraphic system comprising a main circuit, a W 1eatstone-balancecircuithaving its branches connected in the main circuit, a

receiving device inthe bridge of the balance, a condenser connected in aportion of each branch at each side of the bridge, and rendering saidportions'impassable to steady currentsand means associated with thebranches .for adjusting the balance, substantially as described.

4. The combination in a tele raphic circuit with a line conductor, ofparallel conductors forming an extension thereof, a bridge conductorconnecting the parallel conductors, a-

receiving elementin the bridge conductor, a condenser in each of thesaid parallel conductoi s, said condensers being upon opposite sides ofthe bridge conductor, respectively, and a sending element in one of,theparallel conductors at the opposite s des of the bridge conductorfromthe condenser.v

5. In a system for n'ullifying the disturbing effects in telegraphiccircuits organizedfor operation by the normal slowly recurring purrentimpulses of standard Morse transmission, of induced alternating currentsof'relatively: high frequency, the combination of the telegraphlineconductor; with an inductive c1rcuit station section" for the saidhigher fresection for the said normal telegraphiccur-c rents constitutedof the conductlve portions of said parallel branches, and an interposed'bridge or cross conductor joinin saidparaili'el branches at pointsequipotentia with respect to said higher frequency induced currents andbetween the conductive and inductive portions thereof, said conductivelydiscontinuous inductive portions being on different sides of the bridgein their respective parallel branches; and a'receiving telegraphinstrument connected in the said bridge.

6. In a system for nullifying the disturbing effects of induced currentsin telegraphic circuits, the combination of the telegraph line with aninductive circuit station section for said induced currents comprisingtwo parallel branches each composed of a conductive and an inductiveportion in series, a conductive circuit section for the telegraphiccurrents composed of the conductive portions of said parallel branches,and an interposed "bridge or cross-conductor joining points of saidbranches equipotentialwith respect to said induced currents, a receivingtelegraphinstruinent connected in the said bridge, and a transmittinginstrument in one of the condu'ctive branch portions.

7. In a system for nullifying the disturbing effectsin telegraphiccircuits of induced currents of frequency higher than that of theoperating telegraphic currents, the combination with the telegraphline,and a station receiving instrument therefor; of a station circuitarrangement organized as a 'Wheatstone-bah ance, with condensers indiagonally opposite portions of the parallel branches of the saidbalance rendering such ortions conductively discontinuous; the saitreceiving instrument being connected in an operative circuitconstituting the sole conductive path through the VVheatstone-balance,and composed of the bridge and the other two diagonally 0ppositeportions thereof in series, as described herein.

, 8. In a system for nullifying the disturbing effects in telegraphiccircuits of induced currents-having a frequency higher than that of thenormal operating currents, the combination with the telegraph line, anda station receiving-instrument therefor; of a station circuitarrangement comprising two parallel branches and a bridge conductorjoining them and thus organized as a VVheatstone balance; and condensersin die onally opposite portions of the said para lel branches renderingsuch portions conductively discontinuous, and constituting of the othertwo diagonally opposite portions of said branches the bridge conductorthe sole conducting &i 874,826

path through the said balance; the said re- In testimony whereof, Wehave signed our 16 ceiving instrument being connected in the names tothisspeci cation in the presence of bridge-conductor between paralleland e uitwo subscribing Wit 'e}sses, this twenty fifth potential pointsin the paths of said hig er day of May 1906.

5 frequency induced currents, and in series in EDWARD BLAKENEY.

the said sole conducting path of the normal ROBERT E. CHETWOOD JR.elemaphic currents,wherebythe said instru- Witnesses: I

en t is made res onsive to the said normal MILLs E. CASE, currents only,sulistantially as specified. HARRY H. BRIGHAM. I

